I was recently asked to repair one of these.
The traces on the board break easily, so I had to repair some of those, and after a while I got a nice filter sweep and some distortion. But it would always let through some clean signal even when the balance control was fully towards the fuzz side. Turns out an old battery leak had made one of the sides of that pot always have an extra 20k of resistance, while the other side worked like normal.
I traced the pedal and redrew the schematic that was on the inside.
I hope this can help someone else who wants to build or repair one of these.
